Document WO/2004/081408 describes an example of such a hydraulic mount, in which a piston moves in the intermediate chamber and opens or closes an extension of the first restricted passage towards the compensation chamber as a function of the amplitudes of the vibrations to which the anti-vibration mount is subjected, the piston being returned to its normal position by a spring.
Anti-vibration mounts of this type have the drawback of requiring the use of moving unitary parts in the intermediate chamber so that:                there is a risk of jamming,        the assembly of the mount is complex.        